1. Field of the Invention
The present invention pertains to a station-side optical network terminal apparatus, a subscriber-side optical network terminal apparatus, and an optical communication system such as a PON (Passive Optical Network) to perform transmission/reception of information at a high speed by communication using light as a transmission medium.
2. Description of Related Art
In recent years, with popularization of multimedia service such as video service or internet access, installation of an optical communication system which performs communication connection to a subscriber device by FTTB (Fiber to the Building), FTTH (Fiber to the Home), or the like using light as a transmission medium is advanced.
FIG. 1 shows a configuration of a general PON. In an optical communication system serving as a related art of the present invention as shown in FIG. 1, an optical signal from a station-side optical network apparatus OLT (Optical Line Terminal) is passively split and coupled by an optical star coupler serving as a 1-to-multi connection optical split coupler and connected to a plurality of subscriber-side optical network terminal apparatus ONUs (Optical Network Units) installed in an office or the like through optical fibers.
As a system previously applied by the present applicant, an ATM-PON duplex system which forms a duplex configuration between an optical coupler and a subscriber-side optical network terminal apparatus is known. In this system, switching is performed in units of virtual passes or virtual channels on the basis of switching control information, so that high-speed switching to a spare system without adversely affecting a circuit in which a failure does not occur (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2002-57679 (Patent Document 1)).
As an IP (Internet Protocol) telephone access system previously applied by the present applicant, there is known a system which verifies an IP packet by using an address management table, an IP management table, and a subscriber number management table which associates logical link identifiers of subscriber terminal apparatuses and IP addresses of IP telephone terminals with each other. In this manner, a fixed telephone number is prevented from being used beyond a geographical identification area (for example, see JP-A-2006-13639 (Patent Document 2)).
Problems of the related arts described above will be described below.
When a high-speed service of a PON is to be introduced in the optical communication system according to the related art, the service must be continuously performed to a user using an existing service. For this reason, in order to introduce the high-speed communication service, an OLT for the existing service and an OLT for high-speed communication service must be arranged as illustrated in FIG. 2. Thus, in comparison with provision of only the existing service, the cost further increases. In the example in FIG. 2, the OLT for an existing service and the OLT for a high-speed service are denoted as a 1G OLT and a 10G OLT, respectively.
Since optical signals in different wavelength bands are multiplexed in accordance with communication speeds by wavelength division multiplexing (WDM), a usable wavelength path may be difficult to be assured when a communication speed for providing services and the number of applications increase.
The systems in Patent Documents 1 and 2 described above are not made in consideration of provision of services of a plurality of communication speeds. Therefore, in this case, a cost reduction is not considered.